Carbenes and carbenoids are commonly employed for the synthesis of cyclopropane-containing compounds. Here we report the metal-free, intramolecular cyclopropanation of tethered alkenes by free carbenes derived from alkynes to construct structurally unique multicyclic cyclopropanes with perfect atom economy. The nature of the tether influences both the rate of carbene formation and subsequent competing reaction events.
View Article and Find Full Text PDF2:1 adducts arise from the reaction of 2,5-diaryl-1,3,4-oxadiazoles and benzynes generated from the hexadehydro-Diels-Alder (HDDA) reaction. Density functional theory computations support a mechanistic manifold that includes a concerted SAr process. Additionally, the benzyne trapping reaction of 2,5-dimethyl-1,3,4-oxadiazole affords an unusual acylimine-containing 2:1 adduct, which is the first case in which a dearomatized product has arisen from a HDDA reaction.
View Article and Find Full Text PDFTetramethylsilane was recommended for use as an internal reference compound in proton NMR spectroscopy over 60 years ago. However, it is a common practice that researchers reference the analyte chemical shifts to the residual proton resonance in the deuterated solvent in which the spectrum is recorded. Because CDCl is the most commonly used NMR solvent for routine analysis of organic compounds, the effect of various functional groups on the CHCl resonance is important.
View Article and Find Full Text PDFIntroduction: Antipsychotics are commonly used to treat psychotic symptoms and severe mental illnesses. Treatment guidelines recommend antipsychotics be titrated quickly to therapeutic effect in the acute setting but acknowledge that determining the optimal dose is complicated by a delay between treatment initiation and therapeutic response. The purpose of this study was to evaluate antipsychotic titration patterns in an inpatient psychiatric hospital.
View Article and Find Full Text PDFFourier transform ion cyclotron resonance mass spectrometry (FTICR MS) provides the resolution and mass accuracy needed to analyze complex mixtures such as crude oil. When mixtures contain many different components, a competitive effect within the ICR cell takes place that hampers the detection of a potentially large fraction of the components. Recently, a new data collection technique, which consists of acquiring several spectra of small mass ranges and assembling a complete spectrum afterward, enabled the observation of a record number of peaks with greater accuracy compared to broadband methods.
View Article and Find Full Text PDFA new strategy has been developed for characterization of the most challenging complex mixtures to date, using a combination of custom-designed experiments and a new data pre-processing algorithm. In contrast to traditional methods, the approach enables operation of Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) with constant ultrahigh resolution at hitherto inaccessible levels (approximately 3 million FWHM, independent of /). The approach, referred to as OCULAR, makes it possible to analyze samples that were previously too complex, even for high field FT-ICR MS instrumentation.
View Article and Find Full Text PDFThis study analyzes the abstracts and titles of 33,454 business finance, economics, management, and business articles published in ISI (frequently cited) journals during 2013-14. The sample represents 46.4 percent of all papers published in ISI journals in those years, and 52.
View Article and Find Full Text PDFPurpose: To characterize a recently developed model, the retinal degenerate immunodeficient S334ter line-3 rat (SD-Foxn1 Tg(S334ter)3Lav) (RD nude rat), and to test whether transplanted rat fetal retinal sheets can elicit lost responses to light.
Methods: National Institutes of Health nude rats (SD-Foxn1 Tg) with normal retina were compared to RD nude rats with and without transplant for morphology and visual function. Retinal sheets from transgenic rats expressing human placental alkaline phosphatase (hPAP) were transplanted into the subretinal space of RD nude rats between postnatal day (P) 26 and P38.